mythtv backup on upgrade

Should the myth, as packaged, make a backup of my database before
upgrading? On the myth list someone said myth does, but I can't see one
anywhere (from 0.24.2 to 0.25).

A lot went wrong with the upgrade, including an initial failure to
connect to the database (I believe by the deb install scripts) and then
an inability to upgrade the database schema.

Ross